Yet more great replies - thanks !
So, given that I have 2x 1tb hard drives plus a 160gb I might be best off using the smallest for the O/S and programs, then the ohers for my photos and my music - I don't need the utmost speed, but want to keep things simple. I currently am re-using an old copy of xp but have vista home premium coming soon, so will install the 3rd HD then, and can then leave xp untill I know all is working fine.
Next question - multi-booting and different o/s - why ?